Wyoming Edmontosaurus Mummies Show Hoofed Toes

Paleontologists led by Paul Sereno (University of Chicago) described in Science two exceptionally preserved Edmontosaurus annectens “mummies” from a compact “mummy zone” in east‑central Wyoming dating to about 66 million years ago: a late juvenile (~2 years) and an early adult about 12–12.2 m (≈39–40 ft). Instead of fossilized flesh, the specimens’ external anatomy — pebbled skin, a neck/trunk crest, a full row of tail spikes and surprisingly hoofed hind toes — was recorded as sub‑millimeter clay films produced by microbes in a process the authors call “clay templating.” Detailed imaging (optical, CT, electron microscopy and X‑ray spectroscopy) found no original organics, indicating the clay masks preserve a continuous fleshed‑out external profile. The hoofed hind toes are the first documented hooves in any reptile or dinosaur and suggest hooved feet evolved earlier than previously thought, prompting revisions to hadrosaur reconstructions and new functional comparisons to living reptiles. The study shows clay templating can produce exquisite impressions in coarse, oxygenated river sands rather than only in low‑oxygen settings and urges paleontologists to search for clay skin and soft‑tissue impressions as well as bones in the “mummy zone.”